In the previous pdf-note, we have learned about the superficial muscles of the back. In this pdf-note, we will learn more about the deep muscles of the back.

As discussed in the previous pdf-notes, the back region has the following borders:

• The superior border consists of the external occipital protuberance and the superior nuchal line

• The inferior border consists of the sacro-iliac joints, posterior segments of the ilium bones crests, coccyx

• The lateral border is the posterior median line

There are several anatomical regions within the back:

1. Vertebral region (regio vertebralis)

2. Scapular region (regio scapularis)

3. Infrascapular region (regio infrascapularis)

4. Lumbar region (regio lumbalis)

5. Sacral region (regio sacralis)

The muscles of the back are located within these regions. The deep muscles of the back include:

1. First layer

   • Splenius capitis muscle (m. splenius capitis)

     

     

     Splenius capitis muscle
     (m. splenius capitis)

     Origin: spinous processes of the C7-Th3 (sometimes Th4) vertebrae, nuchal ligament

     Insertion: lateral segment of the superior nuchal line, mastoid process of the temporal bone

     Function: with bilateral contraction, it extends the neck and head, with unilateral contraction, it turns and slightly tilts the head ipsilaterally (in its own direction)

     Innervation: posterior branches of the cervical spinal nerves (C2-C3)

     Blood supply: occipital artery, deep cervical artery

   • Splenius cervicis muscle (m. splenius cervicis)

     

     

     Splenius cervicis muscle
     (m. splenius cervicis)

     Origin: spinous processes of the Th3-Th6 vertebrae

     Insertion: transverse processes of the C1-C3 vertebrae

     Function: with bilateral contraction, it extends the neck, with unilateral contraction, it turns and slightly tilts the neck ipsilaterally (in its own direction)

     Innervation: posterior branches of the cervical spinal nerves (C3-C8)

     Blood supply: occipital artery, deep cervical artery

   • Erector spinae muscle (m. erector spinae), which consists of three separate muscles:

     

     

     Iliocostalis muscle (m. iliocostalis)

     

     

     

     

     

     Iliocostalis muscle
     (m. iliocostalis)

     Origin:

     Cervical part arises from the angles of the ribs 3-6

     Thoracic part arises from the angles of the ribs 7-12

     Lumbar part arises from the lateral crest of the sacrum, the medial end of the iliac crest, and the thoracolumbar fascia

     Insertion:

     Cervical part inserts into the transverse processes of the C4-C6 vertebrae

     Thoracic part inserts into the angles of the ribs 1-6, and the transverse process of the C7 vertebra

     Lumbar part inserts into the angles of the ribs 5-12, the transverse processes of the vertebrae L1-L4, as well as the adhering segments of the thoracolumbar fascia

     Function: with bilateral contraction, it extends the vertebral column, with unilateral contraction, it tilts the vertebral column ipsilaterally (in its own direction) and lowers the ribs

     Innervation: posterior branches of spinal nerves (C3-L4)

     Blood supply: deep cervical artery, posterior intercostal arteries, lumbar arteries

     Longissimus muscle (m. longissimus)

     

     

     

     

     Longissimus muscle
     (m. longissimus)

     Origin:

     Cranial part arises from the transverse processes of the C4-Th5 vertebrae

     Cervical part arises from the transverse processes of the Th1-Th5 vertebrae

     Thoracic part arises from the spinous and transverse processes of the L1-L5 vertebrae, median sacral crest, posterior surface of the sacrum, posterior parts of the iliac crest

     Lumbar part arises from the lumbar intermuscular aponeurosis, anteromedial segments of the iliac bone, posterior sacro-iliac ligament

     Insertion:

     Cranial part inserts into the mastoid process of the temporal bone

     Cervical part inserts into the transverse processes of the C2-C6 vertebrae

     Thoracic part inserts into the transverse processes of the T1-Th12 vertebrae, angles of the ribs 7-12

     Lumbar part inserts into the accessory and transverse processes of the L1-L5 vertebrae

     Function: with bilateral contraction, it extends the vertebral column, with unilateral contraction, it tilts the vertebral column ipsilaterally (in its own direction).

     Additional function of the cranial part: with bilateral contraction, it extends the neck and head, with unilateral contraction, it turns and slightly tilts the head ipsilaterally (in its own direction)

     Innervation: posterior branches of spinal nerves (C3-L4)

     Blood supply: deep cervical artery, posterior intercostal, lumbar arteries

     Spinalis muscle (m. spinalis)

     

     

     

     

     Spinalis muscle
     (m. spinalis)

     Origin:

     Cervical part arises from the spinous processes of the C7-Th1 vertebrae, nuchal ligament

     Thoracic part arises from the spinous processes of the Th11-L2 vertebrae

     Insertion:

     Cervical part inserts into spinous processes of the C2-C4 vertebrae

     Thoracic part inserts into spinous processes of the Th2-Th8 vertebrae

     Function: with bilateral contraction, it extends the cervical and thoracic spine; with unilateral contraction, it turns the cervical and thoracic spine ipsilaterally (in its own direction)

     Innervation: posterior branches of spinal nerves (C3-L4)

     Blood supply: deep cervical artery, posterior intercostal arteries

2. Second layer

   Transversospinalis muscle (m. transversospinalis), which consists of three separate muscles:

   

   

   Semispinalis muscle (m. semispinalis)

   

   

   

   

   Semispinalis muscle
   (m. semispinalis)

   Origin:

   Cranial part arises from the articular processes of the C4-C7 vertebrae, transverse processes of the Th1-Th6 vertebrae

   Cervical part arises from the transverse processes of the Th1-Th6 vertebrae

   Thoracic part arises from the transverse processes of the Th6-Th10 vertebrae

   Insertion:

   Cranial part inserts into the between the superior and inferior nuchal lines of the occipital bone

   Cervical part inserts into the spinous processes of the C2-C5 vertebrae

   Thoracic part inserts into the spinous processes of the C6-Th4 vertebrae

   Function: with bilateral contraction, it extends the head, cervical and thoracic spine; with unilateral contraction, it tilts the head, cervical and thoracic spine ipsilaterally (in its own direction) and turns the head, cervical and thoracic spine contralaterally (in the opposite direction)

   Innervation:

   Cranial part: descending branches of the greater occipital nerve (C2) and the C3 spinal nerve.

   Cervical and thoracic parts: posterior branches of spinal nerves (C3-Th12)

   Blood supply: deep cervical artery, posterior intercostal arteries

   Multifidi muscles (mm. multifidi)

   

   

   

   

   Multifidi muscles
   (mm. multifidi)

   Origin:

   Cervical part arises from the superior articular processes of the C4-C7 vertebrae

   Thoracic part arises from the transverse processes of the thoracic vertebrae

   Lumbar part arises from the mastoid processes of the lumbar vertebrae, posterior surface of the sacrum, posterior superior iliac spine, posterior sacro-iliac ligament

   Insertion: spinous processes of the superposed vertebraes (2-5 vertebrae higher)

   Function: with bilateral contraction, it extends the vertebral column, with unilateral contraction, it tilts the vertebral column ipsilaterally (in its own direction) and turns the vertebral column contralaterally (in the opposite direction).

   Innervation: posterior branches of spinal nerves (C3-S1).

   Blood supply: deep cervical artery, posterior intercostal arteries, lumbar arteries

   Rotatores muscles (mm. rotatores)

   

   

   

   

   Rotatores muscles
   (mm. rotatores)

   Origin:

   Short muscles arise from the transverse processes of the Th2-Th12 vertebrae

   Long muscles arise from the transverse processes of the thoracic vertebrae

   Insertion:

   Short muscles insert into the bases of the spinous processes of the superposed vertebrae (1 vertebra higher)

   Long muscles insert into the bases of the spinous processes of the superposed vertebrae (2 vertebrae higher)

   Function: with bilateral contraction, it extends the thoracic spine; with unilateral contraction, it turns the thoracic spine in the opposite direction

   Innervation: posterior branches of thoracic spinal nerves

   Blood supply: deep cervical artery, posterior intercostal arteries, lumbar arteries

3. Third layer

• Interspinales muscles (mm. interspinales)

  

  

  

  

  Interspinales muscles
  (mm. interspinales)

  Origin:

  Cervical part arises from the spinous processes of the C2-C7 vertebrae

  Thoracic part arises from the spinous processes of the Th2, Th11, Th12 vertebrae

  Lumbar part arises from the spinous processes of the L2-L5 vertebrae

  Insertion: into the superposed vertebrae:

  Cervical part inserts into the spinous processes of the C1-C6 vertebrae

  Thoracic part inserts into the spinous processes of the Th1, Th10, Th11 vertebrae

  Lumbar part inserts into the spinous processes of the L1-L4 vertebrae

  Function: extends the vertebral column (which is poorly expressed in the thoracic region, therefore, for the most part in relation to the cervical and lumbar regions)

  Innervation: posterior branches of spinal nerves (C3-L5)

  Blood supply: deep cervical artery, posterior intercostal arteries, lumbar arteries

• Intertransversarii muscles (mm. intertransversarii)

Some sources also list the levatores costarum muscles (mm. levatores costarum) here.

There are also the muscles of the dorsal region of the neck called the suboccipital muscles, which are considered in the corresponding pdf-note.